<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        li{list-style: none;}
        .list li{
            line-height: 45px;
            border: 1px solid #000;
        }
    </style>
</head>
<body>
    <button id="add">新增</button>
    <button id="del">删除</button>
    <div class="list">
        <li>01</li>
        <li>02</li>
        <li>03</li>
        <li>04</li>
        <li>05</li>
        <li>06</li>
    </div>
</body>
<script>
    // HTMLCollection  元素的集合
    // document.getElementsByClassName()
    // document.getElementsByTagName()
    // 元素的集合 会随着页面查找元素的增加或减少自动更新集合
    
    // NodeList    节点的集合
    // document.querySelectorAll()
    // 集合一经获取 就不会再改变

    var add = document.getElementById("add");
    var del = document.getElementById("del");

    var list = document.getElementsByClassName("list")[0];
    var htmlList = list.getElementsByTagName("li");
    console.log(htmlList);
    
    var nodeList = document.querySelectorAll(".list li");
    console.log(nodeList);
    
    add.onclick = function(){
        var li = document.createElement("li");
        li.textContent = "我是新增的li";
        list.appendChild(li);
        
        console.log(htmlList);
        console.log(nodeList);
    }

    del.onclick = function(){
        list.lastElementChild.remove();
        console.log(htmlList);
        console.log(nodeList);
    }



</script>
</html>